1. Field of the Invention
This invention relates to a building construction assembly and, more particularly, to a header for allowing horizontal, non-load bearing headers to vertically fluctuate in relationship to vertical, non-load bearing wall studs to which the headers are attached. By allowing the header freedom of vertical movement, the walls that are fixed to the vertical studs are protected from cracking because the freedom of vertical movement of the header prevents translation of mechanical stresses to the walls caused by downward, environmental forces on the header.
2. Background Information
Prior to the present invention, vertical studs were secured to horizontal headers that secured all the studs in a wall together. The walls, frequently made out of wall board or plaster board, were secured to both the vertical studs and horizontal headers. Joists were usually secured to the top of the header at right angles to the vertical studs and at right angles to the horizontal header. The joists would then extend between the headers. The floor or roof would be secured to the top of the joists. This meant that the floor or roof was rigidly secured to the header which was rigidly secured to the studs. As a consequence, any downward environmental pressures on the floor or roof were translated directly into downward pressure on the the header. This would cause the studs to bow and would also result in the headers applying downward pressure on the wall directly. As a result, the environmental forces applied to the floor or ceiling would be translated into mechanical stress on the walls, which would result in cracks in the walls. The cracks would be further aggravated when the environmental pressure on the floor or ceiling was alleviated because the cracks would expand when the stress was relieved.
Examples of environmental stresses that cause the above kinds of problems are numerous. One of the most common examples involves the weight placed on the headers from the floors above. As a multi-story building is constructed, additional weight is placed on the headers of the lower floors as additional floors are added to the building. The present invention provides a means for the lower floors to absorb the additional stress.
Environmental stresses external to the building itself are also effectively managed by the present invention. For instance, in those parts of the country where it snows, the accummulation of snow fall on the roof can be a source of environmental pressure that will cause the cracking problem in the walls described above. In desert regions of the country, it is common for non-load bearing walls to be made out of metal studs and headers because of the shortage of readily available sources of lumber. In such hot regions of the country, the high temperatures cause the metal to expand. As a result, the wall board attached to the studs and headers is pulled with the expansion causing the walls to crack. The cooling of the metal studs and headers during the cool desert nights and re-expansion during the day aggravates the problem.
Earthquakes are another example of a source of environmental stress that can be managed by the present invention. Building construction technologies for surviving earthquakes are founded on the principle that the building should move with the earthquake. Rigid structures are more likely to suffer damage during an earthquake. The present invention helps prevent cracks in walls caused by earthquakes by permitting the nonload bearing frame to move with the earthquake. Obviously, the invention will not be very effective during a major quake. But for structures situated in earthquake zones that suffer frequent minor quakes, the invention can be of assistance in preventing cracks in the walls.
In addition, those parts of the country that are subject to severe tropical and sub-tropical weather systems, such as those states along the gulf coast, are subject to wide fluctuations in barometric pressure. In the extreme situation in the case of a hurricane, the difference between the barometric pressure on the inside of a house and the atmospheric pressure outside can become so great that the house will actually explode. While the present invention would be of little use in that extreme situation, it would help prevent cracking of the walls during less severe weather conditions that involve substantial fluctuations in barometric pressure.
Furthermore, the environmental pressures on the floors of public buildings can be substantial. For example, the floors of office buildings must support substantial additional weight during office hours as a result of the increased foot traffic. The present invention can accommodate the additional traffic during the day and flex back to its original position when the human load is absent. The prior art would have transferred such fluctuations in environmental pressures to the walls, which would have caused cracks over time. Moreover, the present invention can accommodate increased loads caused by the addition of office furniture and equipment, which the prior art could not without causing strain on and cracking of the walls.